The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kine...The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.展开更多
Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are ...Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.展开更多
An Approximate Voronoi Boundary Network is constructed as the environmental model by way of enlar-ging the obstacle raster. The connectivity of the path network under complex environment is ensured through build-ing t...An Approximate Voronoi Boundary Network is constructed as the environmental model by way of enlar-ging the obstacle raster. The connectivity of the path network under complex environment is ensured through build-ing the second order Approximate Voronoi Boundary Network after adding virtual obstacles at joint-close grids. Thismethod embodies the network structure of the free area of environment with less nodes, so the complexity of pathplanning problem is reduced largely. An optimized path for mobile robot under complex environment is obtainedthrough the Genetic Algorithm based on the elitist rule and re-optimized by using the path-tightening method. Sincethe elitist one has the only authority of crossover, the management of one group becomes simple, which makes forobtaining the optimized path quickly. The Approximate Voronoi Boundary Network has a good tolerance to the im-precise a priori information and the noises of sensors under complex environment. Especially it is robust in dealingwith the local or partial changes, so a small quantity of dynamic obstacles is difficult to alter the overall character ofits connectivity, which means that it can also be adopted in dynamic environment by fusing the local path planning.展开更多
Path planning is one of the most important problems in the design of a mobile robot.A novel approach called generalized Voronoi diagrams(GVD)may deal with this matter.First,a method was introduced to normalize the obs...Path planning is one of the most important problems in the design of a mobile robot.A novel approach called generalized Voronoi diagrams(GVD)may deal with this matter.First,a method was introduced to normalize the obstacles and present efficient techniques for generating GVDs.Then a best path searching algorithm was presented.Examples implemented were given to indicate the availability of the mentioned algorithms.The approaches in this paper can also be used in applications including visualization,spatial data manipulation,etc.展开更多
Electron probe microanalysis and SEM were employed to study the phase equilibria and diffusion paths in C Ni 8Ta, C Ni 3Ta, C Ni 2Ta diffusion couples after annealed at 1100 ℃ for 120 h or at 1200 ℃ for 120 h ...Electron probe microanalysis and SEM were employed to study the phase equilibria and diffusion paths in C Ni 8Ta, C Ni 3Ta, C Ni 2Ta diffusion couples after annealed at 1100 ℃ for 120 h or at 1200 ℃ for 120 h and then at 1100 ℃ for 24 h. Attempt was made to use the calculated stability diagram of carbon activity to explain the experimental observations. The phases formed in the diffusion layers were all in the prediced ranges.展开更多
基金Financial supports by the NSFC(China)under the research projects(No.50071058 and No.59725101)by the CAS(China)-CNR(Italy)under an international collaboration agreement are gratefully acknowledged.
文摘The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.
文摘Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.
基金Project (60234030) supported by the National Natural Science Foundation of China
文摘An Approximate Voronoi Boundary Network is constructed as the environmental model by way of enlar-ging the obstacle raster. The connectivity of the path network under complex environment is ensured through build-ing the second order Approximate Voronoi Boundary Network after adding virtual obstacles at joint-close grids. Thismethod embodies the network structure of the free area of environment with less nodes, so the complexity of pathplanning problem is reduced largely. An optimized path for mobile robot under complex environment is obtainedthrough the Genetic Algorithm based on the elitist rule and re-optimized by using the path-tightening method. Sincethe elitist one has the only authority of crossover, the management of one group becomes simple, which makes forobtaining the optimized path quickly. The Approximate Voronoi Boundary Network has a good tolerance to the im-precise a priori information and the noises of sensors under complex environment. Especially it is robust in dealingwith the local or partial changes, so a small quantity of dynamic obstacles is difficult to alter the overall character ofits connectivity, which means that it can also be adopted in dynamic environment by fusing the local path planning.
基金supported by Beijing Natural Science Foundation (contact no.4062010)
文摘Path planning is one of the most important problems in the design of a mobile robot.A novel approach called generalized Voronoi diagrams(GVD)may deal with this matter.First,a method was introduced to normalize the obstacles and present efficient techniques for generating GVDs.Then a best path searching algorithm was presented.Examples implemented were given to indicate the availability of the mentioned algorithms.The approaches in this paper can also be used in applications including visualization,spatial data manipulation,etc.
文摘Electron probe microanalysis and SEM were employed to study the phase equilibria and diffusion paths in C Ni 8Ta, C Ni 3Ta, C Ni 2Ta diffusion couples after annealed at 1100 ℃ for 120 h or at 1200 ℃ for 120 h and then at 1100 ℃ for 24 h. Attempt was made to use the calculated stability diagram of carbon activity to explain the experimental observations. The phases formed in the diffusion layers were all in the prediced ranges.
